Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a catalyst for low-temperature catalytic oxidation of formaldehyde, which has low reaction temperature and high reaction activity, and a preparation method and application thereof.
The purpose of the invention can be realized by the following technical scheme:
a catalyst for low-temp catalytic oxidation of formaldehyde contains CuOxAnd activated carbon, wherein the molar ratio of Cu to C is (3.0-15.0): (85.0-97.0).
Further, the molar ratio of Cu to C is 3.0: 97.0.
Further, the molar ratio of Cu to C is 7.0: 93.0.
Further, the molar ratio of Cu to C is 11.0: 89.0.
Further, the molar ratio of Cu to C is 15.0: 85.0.
A method for preparing the catalyst for the low-temperature catalytic oxidation of formaldehyde, which comprises the following steps:
(1) adding Cu (NO) in a molar ratio3)2·3H2Dissolving O, and mixing with activated carbon under stirring to react to obtain a reaction solution;
(2) heating the reaction solution, and continuously stirring until the liquid is evaporated to dryness to obtain a catalyst;
(3) drying the catalyst in N2And roasting in the atmosphere to obtain the catalyst for low-temperature catalytic oxidation of formaldehyde.
Because the copper component is loaded on the surface of the activated carbon, N is in inert atmosphere2After the catalyst is roasted at 600 ℃, organic micromolecules and C steam can be evaporated from the surface of the activated carbon, so that the copper component can be slowly reduced, oxygen-containing species on the surface of the activated carbon can be gradually reduced, and copper species with high dispersion and low interaction are formed, so that the low-temperature oxidation activity of the catalyst is effectively increased.
Further, the rotation speed of the stirring in the step (1) is 320-; the temperature rise in the step (2) is 58-63 ℃.
Further, the drying temperature in the step (3) is 110-125 ℃, and the drying time is 8-16 h; the roasting temperature is 600-700 ℃, and the roasting time is 1.5-2.5 h.
The application of the catalyst for the low-temperature catalytic oxidation of formaldehyde is disclosed, and the catalyst is applied to the low-temperature catalytic oxidation of formaldehyde.
Further, the catalyst needs to be in N before catalytic oxidation2Pretreating for 20-40min at the temperature of 180 ℃ and 220 ℃ in the atmosphere; the reaction components of the formaldehyde low-temperature catalytic oxidation comprise 600ppm HCHO and 10 vol.% O2And balance gas N2On the contraryThe temperature should be 90-130 ℃. Preferably 120-130 ℃.
The catalyst is in inert atmosphere N2In the next pretreatment process, the activated carbon can slowly reduce copper oxide species, and meanwhile, oxygen-containing species on the surface of the activated carbon can be gradually reduced to form copper species with high dispersion and low interaction, so that the low-temperature oxidation activity of the catalyst is effectively increased.
Compared with the prior art, the Cu/C catalyst adopted by the invention is about 600 ℃, and N is2The high-temperature reduction treatment under the atmosphere can be further characterized by the catalyst, and the oxygen species in the activated carbon are gradually separated out to the surface of the catalyst at the temperature and interact with the copper component to form copper species in a high dispersion state. And some organic small molecules can be evaporated from the surface of the activated carbon, and C steam can further reduce copper species to form rich Cu+And Cu0Species, the presence of which facilitates the dehydrogenation of formaldehyde to form CO, producing CuO with rapid and highly dispersed COxReaction to CO2Thereby remarkably reducing the reaction temperature of the catalyst.
Detailed Description
The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.
Example 1
A catalyst for low-temp catalytic oxidation of formaldehyde is prepared through immersing activated carbon in copper nitrate solution, and adding N2The catalyst is prepared by high-temperature reduction activation under the atmosphere, and the composition in the catalyst is calculated according to the molar ratio of copper atoms to carbon contained in the catalyst, and the specific formula is as follows: the preparation method of the Cu/C-3.0/97.0 concrete comprises the following steps:
7.5g of Cu (NO)3)2·3H2Dissolving O in a beaker filled with 26mL of deionized water and a magnetic stirrer, placing the beaker on a magnetic heating stirrer, adjusting the rotating speed of the stirrer to 320-Stirring for 2 hr, adjusting the temperature of the magnetic heating stirrer to 58-63 deg.C, stirring and heating until no liquid is observed, drying the prepared catalyst at 120 deg.C for 12 hr, and adding N2Roasting for 2 hours at 650 ℃ in the atmosphere to obtain the catalyst A for low-temperature catalytic oxidation of formaldehyde.
The catalyst A obtained in the above example and used for catalytic oxidation of HCHO under mild conditions was crushed and sieved out to 20-40 mesh for use.
Activity test of catalyst A for catalytic oxidation of HCHO under mild conditions was conducted in a miniature quartz tube fixed-bed reactor in which 0.5g of catalyst A (40-60 mesh) for catalytic oxidation of HCHO in a room was mixed with an equal volume of quartz sand and fixed to the middle section of a reaction tube (inner diameter 6mm) at N2After pretreatment at 200 ℃ for 30min under an atmosphere (flow rate: 30mL/min), the temperature was lowered to room temperature, and then a reaction gas (content: 600ppm HCHO, 10 vol.% O) was switched2And balance gas N2Total flow rate is 50mL/min), formaldehyde gas is mixed with balance gas N2Flow through a paraformaldehyde bubbler (heated in a water bath at 36 ℃ C.). The reaction temperature is 90 ℃, 100 ℃, 110 ℃, 120 ℃ and 130 ℃, and each temperature point is subjected to online measurement after reaction for 30 min: separating reaction tail gas by carbon molecular sieve chromatographic column, passing through nickel converter, and detecting formaldehyde, CO and CO by FID detector2Respectively recording the HCHO conversion rate and CO corresponding to the detected HCHO under the conditions of reaction temperature of 90 ℃, 100 ℃, 110 ℃, 120 ℃ and 130 DEG C2The selectivities, the results obtained are shown in the following table:
from the above table it can be seen that the catalyst exhibits a certain catalytic oxidation activity of HCHO at least 90 ℃ and complete catalytic oxidation of HCHO at 130 ℃ and CO2The selectivity is more than 99 percent.
Example 2
A catalyst for low-temp catalytic oxidation of formaldehyde is prepared through immersing activated carbon in copper nitrate solution, and adding N2High under atmosphereThe catalyst is prepared by warm reduction activation, and the composition in the catalyst is calculated according to the molar ratio of copper atoms to carbon contained in the catalyst, and the specific formula is as follows: the preparation method of the Cu/C-7.0/93.0 concrete comprises the following steps:
18.2g of Cu (NO)3)2·3H2Dissolving O in a beaker filled with 63mL of deionized water and a magnetic stirrer, placing the beaker on a magnetic heating stirrer, adjusting the rotating speed of the stirrer to 320-380r/min, adding 10g of activated carbon into the solution after the copper nitrate crystals are completely dissolved, then continuing stirring for 2h, adjusting the temperature of the magnetic heating stirrer to 58-63 ℃, then continuing stirring and heating until no liquid is seen, drying the prepared catalyst at 120 ℃ for 12h, and adding N into the beaker2Roasting for 2 hours at 650 ℃ in the atmosphere to obtain the catalyst B for low-temperature catalytic oxidation of formaldehyde.
The catalyst B obtained in the above example for catalytic oxidation of HCHO under mild conditions was crushed and sieved out to 20-40 mesh for use.
Activity test of catalyst B for catalytic oxidation of HCHO under mild conditions was conducted in a miniature quartz tube fixed-bed reactor in which 0.5g of catalyst B (40-60 mesh) for catalytic oxidation of HCHO in a room was mixed with an equal volume of quartz sand and fixed to the middle section of a reaction tube (inner diameter 6mm) at N2After pretreatment at 200 ℃ for 30min under an atmosphere (flow rate: 30mL/min), the temperature was lowered to room temperature, and then a reaction gas (content: 600ppm HCHO, 10 vol.% O) was switched2And balance gas N2Total flow rate is 50mL/min), formaldehyde gas is mixed with balance gas N2Flow through a paraformaldehyde bubbler (heated in a water bath at 36 ℃ C.). The reaction temperature is 90 ℃, 100 ℃, 110 ℃, 120 ℃ and 130 ℃, and each temperature point is subjected to online measurement after reaction for 30 min: separating reaction tail gas by carbon molecular sieve chromatographic column, passing through nickel converter, and detecting formaldehyde, CO and CO by FID detector2Respectively recording the HCHO conversion rate and CO corresponding to the detected HCHO under the conditions of reaction temperature of 90 ℃, 100 ℃, 110 ℃, 120 ℃ and 130 DEG C2The selectivities, the results obtained are shown in the following table:
from the above table it can be seen that the catalyst is fully catalytic for HCHO at 120 ℃ and CO2The selectivity reaches 100 percent.
The catalyst B for indoor catalytic oxidation of HCHO obtained in the example was subjected to kinetic activity evaluation, and a micro quartz tube was placed in a reaction furnace at 120 ℃ while maintaining the reaction temperature constant, which corresponds to the conversion of HCHO and CO at different times2The selectivities are given in the following table:
no decrease in activity was observed after 65 hours of continuous operation.
Example 3
A catalyst for low-temp catalytic oxidation of formaldehyde is prepared through immersing activated carbon in copper nitrate solution, and adding N2The catalyst is prepared by high-temperature reduction activation under the atmosphere, and the composition in the catalyst is calculated according to the molar ratio of copper atoms to carbon contained in the catalyst, and the specific formula is as follows: the preparation method of the Cu/C ═ 11.0/89.0 specifically comprises the following steps:
30.0g of Cu (NO)3)2·3H2Dissolving O in a beaker filled with 103mL of deionized water and a magnetic stirrer, placing the beaker on a magnetic heating stirrer, adjusting the rotating speed of the stirrer to 320-380r/min, adding 10g of activated carbon into the solution after the copper nitrate crystals are completely dissolved, then continuously stirring for 2h, adjusting the temperature of the magnetic heating stirrer to 58-63 ℃, then continuously stirring and heating until no liquid is seen, drying the prepared catalyst at 120 ℃ for 12h, and adding N2Roasting for 2 hours at 650 ℃ in the atmosphere to obtain the catalyst C for low-temperature catalytic oxidation of formaldehyde.
The catalyst C obtained in the above example for catalytic oxidation of HCHO under mild conditions was crushed and sieved out to 20-40 mesh for use.
Activity test of catalyst C for catalytic oxidation under mild conditions of HCHO was carried out in a miniature quartz tube fixed bed reactor using 0.5g for indoor HMixing CHO catalytic oxidation catalyst C (40-60 mesh) with equal volume of quartz sand, fixing to the middle section of a reaction tube (inner diameter 6mm) in N2After pretreatment at 200 ℃ for 30min under an atmosphere (flow rate: 30mL/min), the temperature was lowered to room temperature, and then a reaction gas (content: 600ppm HCHO, 10 vol.% O) was switched2And balance gas N2Total flow rate is 50mL/min), formaldehyde gas is mixed with balance gas N2Flow through a paraformaldehyde bubbler (heated in a water bath at 36 ℃ C.). The reaction temperature is 90 ℃, 100 ℃, 110 ℃, 120 ℃ and 130 ℃, and each temperature point is subjected to online measurement after reaction for 30 min: separating reaction tail gas by carbon molecular sieve chromatographic column, passing through nickel converter, and detecting formaldehyde, CO and CO by FID detector2Respectively recording the HCHO conversion rate and CO corresponding to the detected HCHO under the conditions of reaction temperature of 90 ℃, 100 ℃, 110 ℃, 120 ℃ and 130 DEG C2The selectivities, the results obtained are shown in the following table:
example 4
A catalyst for low-temp catalytic oxidation of formaldehyde is prepared through immersing activated carbon in copper nitrate solution, and adding N2The catalyst is prepared by high-temperature reduction activation under the atmosphere, and the composition in the catalyst is calculated according to the molar ratio of copper atoms to carbon contained in the catalyst, and the specific formula is as follows: the preparation method of the Cu/C-15.0/85.0 concrete comprises the following steps:
42.8g of Cu (NO)3)2·3H2Dissolving O in a beaker filled with 147mL of deionized water and a magnetic stirrer, placing the beaker on a magnetic heating stirrer, adjusting the rotating speed of the stirrer to be 320-380r/min, adding 10g of activated carbon into the solution after the copper nitrate crystals are completely dissolved, then continuously stirring for 2h, adjusting the temperature of the magnetic heating stirrer to be 58-63 ℃, then continuously stirring and heating until no liquid is seen, drying the prepared catalyst for 12h at 120 ℃, and adding N2Roasting for 2 hours at 650 ℃ in the atmosphere to obtain the catalyst D for low-temperature catalytic oxidation of formaldehyde.
The catalyst D obtained in the above example for catalytic oxidation of HCHO under mild conditions was crushed and sieved out to 20-40 mesh for use.
Activity test of catalyst D for catalytic oxidation of HCHO under mild conditions was conducted in a miniature quartz tube fixed-bed reactor in which 0.5g of catalyst D (40-60 mesh) for catalytic oxidation of HCHO in a room was mixed with an equal volume of quartz sand and fixed to the middle section of a reaction tube (inner diameter 6mm) at N2After pretreatment at 200 ℃ for 30min under an atmosphere (flow rate: 30mL/min), the temperature was lowered to room temperature, and then a reaction gas (content: 600ppm HCHO, 10 vol.% O) was switched2And balance gas N2Total flow rate is 50mL/min), formaldehyde gas is mixed with balance gas N2Flow through a paraformaldehyde bubbler (heated in a water bath at 36 ℃ C.). The reaction temperature is 90 ℃, 100 ℃, 110 ℃, 120 ℃ and 130 ℃, and each temperature point is subjected to online measurement after reaction for 30 min: separating reaction tail gas by carbon molecular sieve chromatographic column, passing through nickel converter, and detecting formaldehyde, CO and CO by FID detector2Respectively recording the HCHO conversion rate and CO corresponding to the detected HCHO under the conditions of reaction temperature of 90 ℃, 100 ℃, 110 ℃, 120 ℃ and 130 DEG C2The selectivities, the results obtained are shown in the following table:
in summary, CuO is usedxthe/C catalyst shows relatively excellent catalytic activity for the low-temperature oxidation of formaldehyde. The catalyst has mild reaction condition, can completely convert formaldehyde at 120 ℃, and has CO2The selectivity of the catalyst is more than 99.8 percent. In addition, the preparation method of the catalyst is simple, and easy to enlarge and industrialize.
Comparative example 1
A catalyst for low-temp catalytic oxidation of formaldehyde is prepared through immersing activated carbon in copper nitrate solution, and adding N2The catalyst is prepared by high-temperature reduction activation under the atmosphere, and the composition in the catalyst is calculated according to the molar ratio of copper atoms to carbon contained in the catalyst, and the specific formula is as follows: the preparation method of the Cu/C-30.0/70.0 concrete comprises the following steps:
86.3g of Cu (NO)3)2·3H2Dissolving O in a beaker filled with 357mL deionized water and a magnetic stirrer, placing the beaker on a magnetic heating stirrer, adjusting the rotating speed of the stirrer to 320-2Roasting for 2 hours at 650 ℃ in the atmosphere to obtain the catalyst E for low-temperature catalytic oxidation of formaldehyde.
The catalyst E obtained in the above example for catalytic oxidation of HCHO under mild conditions was crushed and sieved out to 20-40 mesh for use.
Activity test of catalyst E for catalytic oxidation of HCHO under mild conditions was conducted in a miniature quartz tube fixed-bed reactor in which 0.5g of catalyst E (40-60 mesh) for catalytic oxidation of HCHO in a room was mixed with an equal volume of quartz sand and fixed to the middle section of a reaction tube (inner diameter 6mm) at N2After pretreatment at 200 ℃ for 30min under an atmosphere (flow rate: 30mL/min), the temperature was lowered to room temperature, and then a reaction gas (content: 600ppm HCHO, 10 vol.% O) was switched2And balance gas N2Total flow rate is 50mL/min), formaldehyde gas is mixed with balance gas N2Flow through a paraformaldehyde bubbler (heated in a water bath at 36 ℃ C.). The reaction temperature is 120 ℃, 140 ℃, 160 ℃, 180 ℃ and 200 ℃, and each temperature point is subjected to online measurement after reaction for 30 min: separating reaction tail gas by carbon molecular sieve chromatographic column, passing through nickel converter, and detecting formaldehyde, CO and CO by FID detector2Respectively recording the HCHO conversion rate and CO corresponding to the detected HCHO under the conditions of reaction temperature of 120 ℃, 140 ℃, 160 ℃, 180 ℃ and 200 DEG C2The selectivities, the results obtained are shown in the following table:
it can be seen from the comparative example that when the copper content is too high, the activity of the catalyst is significantly reduced, the temperature is 200 ℃, the conversion of formaldehyde is close to 100%, and the CO content is slightly higher. The characterization of the catalyst shows that when the copper content is too high, the activated carbon is completely wrapped by the copper, so that the catalyst cannot be fully reduced at 600 ℃ under a nitrogen atmosphere, and the copper oxide particles are seriously aggregated, so that the catalytic performance of the copper oxide is only reflected, and the effect of the activated carbon cannot be reflected.
The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.